1. Field of the Invention
The present invention relates to a variable capacity type vane compressor comprising a cylinder having an oblong cylinder bore with a pair of side plates coupled on either side of the cylinder to close the cylinder bore, a rotor with a plurality of radially arranged vanes rotatably inserted in the cylinder to provide compression chambers in a space between the cylinder inner surface and the rotor outer surface, gas inlet means for introducing oil containing gas into the compression chambers, gas outlet means for discharging compressed gas from the compression chamber into an output chamber, and means for varying a ratio of the capacity of the compressor by bringing the compression chamber to a state where a full compression is not effected, and accordingly, the output capacity is decreased.
2. Description of the Related Art
A variable capacity type vane compressor is used in many applications, and in particular, for a compressor for compressing refrigerant gas in an air conditioning system in an automobile. A relatively large output capacity is required for such a compressor when the air conditioning system is operating in a high cooling mode to lower the temperature in the cabin of the automobile, but such a large output capacity may not be necessary when the air conditioning system is operating in a normal cooling mode to maintain a comfortable temperature once the temperature in the cabin has reached such a level. Therefore, at this time, desirably the capacity of the compressor is reduced.
Japanese Unexamined Patent Publication No. 61-76792, including the inventors of the present case, disclosed a variable capacity type vane compressor comprising a capacity control disk rotatably arranged at an interface between the front side plate and the cylinder/rotor and having an axially extending port (hereinafter second port). The front side plate has a first axially extending port for introducing gas to be compressed, which together with the second axially extending port of the capacity control disk, constitutes a continuous inlet passage for gas to be compressed. By rotational controlling the position of the capacity control disk, the flow area of the inlet passage can be varied to change the capacity of the compressor.
The actuator provided for moving the capacity control disk comprises a spool cylinder provided in the front side plate and a spool, to which the capacity control disk is connected, inserted in this spool cylinder for reciprocal movement. First and second working chambers are formed in the spool cylinder on opposite sides of the spool, and an oil passage connects the second working chamber to an oil separating chamber near the bottom thereof to introduce liquid oil under output pressure into the second working chamber. A valve is arranged in the oil passage and is operated by a change of the pressure of the inlet gas to open or close the oil passage; the pressure changes being caused by changes in the load of the refrigerating system. A leak passage connects the second working chamber to the inlet chamber to relieve the oil pressure in the second working chamber when the valve is closed.
The first working chamber is connected, via a narrow passage, to the vane inserting grooves in the rotor, which in turn are connected, via the bearing lubricating passage, to the oil separating chamber near the bottom thereof. Therefore, oil is delivered from the oil separating chamber under the output pressure but the pressure is released when oil passes through the vane inserting grooves and the bearing lubricating passage, and oil under an intermediate pressure is supplied to the first working chamber.
A problem occurs in this vane compressor in that oil in the first working chamber tends to flow back when the valve opens the oil passage and the oil under output pressure flows into the second working chamber. This causes an undesirably rapid motion of the spool and the capacity control disk and an abrupt change in the capacity of the compressor of from low to high. Also, when the valve closes the oil passage, oil in the second working chamber is relieved into the inlet chamber via the leak passage and the pressure in the second working chamber is decreased, causing an undesirably rapid motion of the spool and the capacity control disk and an abrupt change in the capacity of the compressor of from high to low. This induces an undesirable variation in the temperature of air in the evaporator in the system and reduces the air conditioning effect.